Stemming device



April 20, 1965 M. NATLAND STEMMING DEVICE 2 Sheets-Sheet 1 Filed Aug. 6, 1959 IN V EN TOR.

0 m M; mx w N v A April 20, 1965 M. L. NATLAND STEMMING DEVICE 2 Sheets-Sheet 2 Filed Aug. 6, 1959 a 3 M i mfi M; m

United States Patent 3,179,049 STEMIWING DEVICE Manley L. Natland, Rolling Hills, Calif., assignor to Richfield Gil Corporation, Los Angeles, Calif., a corporation of Delaware Filed Aug. 6, 1959, Ser. No. 831,992 4 Claims. (Cl. 102-226) This invention relates to the subterranean detonation of an explosive device. More particularly, this invention relates to a stemming means for preventing up-hole blast from a subterranean nuclear explosion through a hole bored to facilitate placing the explosive device underground.

It has recently been found that nuclear explosive devices, i.e., atomic and hydrogen bombs, can be deto nated beneath the surface of the earth. The results of an underground explosion of this nature are described in the University of California Research Laboratories Report No. 5124, entitled Rainier Operation Plumbbob, February 4, 1958. Since this discovery several methods have been devised for utilizing these subterranean explosions for commercial purposes, such as for the re covery of mineral or petroleum deposits. Examples of such methods and of explosive devices suitable for subterranean explosives of the type herein contemplated are shown in my co-pending applications Serial No. 707,058, filed January 3, 1958, now abandoned, and Serial No. 706,960, filed January 3, 1958. See also my application Serial No. 752,282, filed July 31, 1958.

One of the inherent difficulties in an underground nuclear explosion is the tendency of the explosion to blow out radioactive material through the placement bore hole and to expend part of the force of the explosion upward or outward through the bore hole, thus decreasing the explosive force available for the intended pur pose at the blast site. The collapse of the casing by the disrupted strata adjacent .the bore hole effectively plugs the bore hole, however, the collapse of the casing does not readily occur unless the travel of the shock wave through the bore hole is retarded by some means. Concrete plugs or sand bags have been provided in the placement hole above or behind the explosive device for the purpose of stemming the underground nuclear explosion to prevent up-hole blast. leans for detonating the explosive device such as a firing cable are extended through the plug to the explosive device. In the case of a vertical placement hole after the explosive device and plug are set in position the cast concrete plug is not removable and access to the explosive nuclear device may be had only through the firing cable or by drilling through the concrete plug. When the explosive device fails to explode adjustments or corrections which may be necessary with the explosive device itself cannot be made due to the permanent nature of the plug. Consequently, in prior art arrangements because of the permanent nature of the plug, the nuclear explosive device would be wasted should the detonation fail.

Therefore, an object of my present invention is to provide stemming means for an underground ncle-ar explosion which permit access to the explosive device in the event access is required after the explosive device and stemming means are positioned in the bore hole.

It is a further object of my invention to provide removable stemming means for an underground nuclear explosion which permit access to the explosive device in the event the device fails to explode.

It is also an object of my invention to provide stemming means for an underground nuclear explosion which facilitate the collapse of the bore hole casing and permit access to the explosive device after placement of the ex- 3,179,049 Patented Apr". 20, 1965 plosive device and stemming means in position down a. bore hole.

Briefly stated, my invention relates .to stemming an underground nuclear explosion with a relatively dense material capable of retarding the explosive forces in the form of a plug adapted to be lowered into and removed from the placement bore hole and having a passageway through which detonating means can be connected to the explosive device therebelow.

In order to more fully describe the present invention, reference is made to the accompanying drawing, wherein FIGURE 1 shows a bore hole traversing the oil-bearing strata, having positioned at its lower terminus a nuclear explosive device and stemming means with lowering apparatus therefor;

FIGURE 2 shows an enlarged view of the stemming device shown in the bore hole of FIGURE 1;

FIGURE 3 is a transverse cross-sectional view of the stemming device taken on section 3-3 of FIGURE 2 showing the firing cable positioned within the longitudinal passageway of the stemming device;

FXGURE 4 represents a modification of my invention showing a modified stemming device positioned within a bore hole;

FIGURE 5 is a transverse cross-sectional view of the stemming evice shown in FIGURE 4.

With reference to the drawings, the invention is illustrated in an underground petroliferous formation having a cased bore hole 3 extending downward through the formation. For illustrative purposes, a nuclear explosive device 5 is shown positioned in a limestone firing medium 7 beneath the petroliferous formation 5, and is lowered into position by hoist 9 on hoisting cable 13.. The nuclear device 6 is detonated by tiring controls housed in trailer 13 through multi-conductor firing cable 15. Conventional pulley rigs 17a and 17b are utilized to facilitate the lowering and raising of hoisting cable 11 and firing cable 15 into the bore hole. Rig 17a and hoisting cable 11 are preferably of heavy construction to accommodate the weight of the explosive device and stemming apparatus described below.

In order to prevent up-hole blast with the ejection of materials out the upper end of the bore hole and the venting of radioactive materials into the atmosphere, stemming apparatus is positioned in the bore hole 3 above the nuclear explosive device 5. The stemming apparatus of my invention comprises one or more reinforced concrete plugs 21 which may conveniently be lowered into the bore hole on hoisting cable 11 through appropriate linkage as hereinbelow described.

As best viewed in FIGURE 2, the plug 21 has a concrete body portion 23 with tensile reinforcing members 25, formed in the conventional manner of casting concrete around reinforcing bars or rods. The reinforcing members 25 preferably protrude beyond the concrete body 23 on both ends 27 to facilitate linking with the hoisting cable 11. These end portions 27 of the reinforcement members are provided with openings 29 through which removable bolts 31 provide suitable connections for fastening the plug 21 to the hoisting cable 11 as by looping cable ends 33 around bolts 31 and securing the loop to the cable with cable clamps 35.

A channel for conducting the firing cable 15 past the concrete plug 21 is made by providing a longitudinal slot or keyway 37 in plug 21. Keyway 37 not only facilitates the passage of firing cable 15 by plug 21 to the nuclear device 5 but also protects cable 15 from being crushed or otherwise damaged by plug 21. The firing cable 15 may be locked in the keyway 37 by pins 39 placed through holes 41 provided transversely in a chordal direction across the keyway 37.

Reinforcement of concrete plug 21 with continuous =3 steel bars or other high strength material known to those skilled in the art may be utilized to furnish tensile strength in the plug so that the concrete is not unduly stressed in tension. It is to be understood that although I have utilized concrete in the particular example shown, other materials such as sand, capable of temporarily retarding the travel of the shock wave through the bore hole, are within the scope and spirit of my invention.

As shown in FIGURE 1, two plugs 21 may be linked to the hoisting cable 11. Depending on the size and the depth of the nuclear explosion and the degree of radioactive containment required, one or more of such plugs may be employed in the stemming apparatus. A sufficient number of plugs should be used to slow the shock Wave in the well column in relation to the speed of movement of the wave through the rock, so that the casing collapses under pressure from the surrounding formation at a point above the deepest plug. The timely collapse of the casing not only prevents ejection of material through the top of the bore hole 3 but also prevents the venting of radioactive materials into the atmosphere.

If collapse of the casing occurs below the lowest plug of my stemming device, the plugs can be pulled out of the bore hole and used again by providing a shear pin in place of the lower linkage bolt 31. In one modification of my invention, shear pins of varying shear characteristics are utilized on the plug linkages to allow recovery of all plugs above the casing collapse. This is accomplished by providing progressively weaker shear pins on lower plugs.

In a modification of the stemming plug of my invention, the reinforcement and linkage means are varied as illustrated in FIGURES 4 and 5. A steel tubular mem her or pipe 43 may be used to reinforce the concrete body 45 of the stemming plug. The pipe 43 may be positioned in the concrete body by any method known to those skilled in the art as by casting the concrete around the pipe. In order to add to the mass of the plug, the interior of the pipe 43 may also be filled with concrete as shown in FIGURE 4 at 47. In this modified stemming plug the pipe 43 absorbs the tensile stress put on the plug.

A leaded cable connection 48 attached to pipe 43 with a bolt 49 provides linkage of my modified plug to the hoisting cable 51. Connector tube 53 is formed with a narrowed end 55 in which end strands of cable 51 are spread with molten lead. Bolt 50 may be used as a shear pin having varying shearing characteristics to provide for release of plugs above the casing collapses as heretofore mentioned.

Keyway 59 provides for passage of firing cable 15 past plug body 45. Firing cable 15 may be maintained in keyway 59 by transversely positioned pin as shown in FIGURE 3 or by fastening to hoisting cable 51 with ring 61.

Although I have described my invention with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be made without departing from the spirit and the scope of my invention as hereinafter claimed.

I claim:

1. A stemming device of the character described comprising an elongated body, said body being of concrete with metallic means extending longitudinally therethrough forming ends of said body, means adapting each of said ends for attachment to a cable, and said body having an elongated open-ended longitudinally extending slot therethrough for receiving a conduit.

2. A device as set forth in claim 1 in which said metallic means comprises two metallic bars extending through said concrete.

3. A device as set forth in claim 1 in which said metallic means is in the form of a metallic tube extending centrally through said concrete.

4. A device as set forth in claim 1 including a pin mounted on said body and extending transversely through said slot to confine conduit in said slot.

References Cited in the file of this patent UNITED STATES PATENTS 793,128 Gardner June 27, 1905 1,248,689 McAvoy Dec. 4, 1917 1,979,802 Kinley Nov. 6, 1934 2,040,581 Voortrnann Mar. 12, 1936 2,144,208 Van Meter Ian. 17, 1939 2,646,845 Schillinger July 28, 1953 2,921,519 Martin Ian. 19, 1960 OTHER REFERENCES UCRL5124, University of California Radiation Laboratory, Feb. 4, 1958. Pages 520, 26, 27.

UCRL-5677 Plowshare Series, Proceedings of the Second Plowshare Symposium. May 1315, 1959. Lawrence Radiation Laboratory, Lawrence, Calif. Part III, May 14, 1959. 

1. A STEMMING DEVICE OF THE CHARACTER DESCRIBED COMPRISING AN ELONGATED BODY, SAID BODY BEING OF CONCRETE WITH METALLIC MEANS EXTENDING LONGITUDINALLY THERETHROUGH FORMING ENDS OF SAID BODY, MEANS ADAPTING EACH OF SAID ENDS FOR ATTACHMENT TO A CABLE, AND SAID BODY HAVING AN ELONGATED OPEN-ENDED LONGITUDINALLY EXTENDING SLOT THERETHROUGH FOR RECEIVING A CONDUIT. 